Method of temperature control in nitration of hydrocarbons



v L. A. STENGEL METHOD OF TEMPERATURE CONTROL IN June 20, 1950 NITRATION0F HYDROCARBONS 3 Sheets-Sheet 1 Filed June 8, 1949 INVENTOR June 20,1950 A.l sTENGEL METHOD OF' TEMPERATURE CONTROL IN NITRATION oFHYDRocARBoNs 3 Sheets-Sheet 2 Filed June 8. 1949 F IG. II

INVENTOR June 20, 1950 l.. A. STENGEL 2,512,587

METHOD 0F TEMPERATURE CONTROL IN NITRATION 0F HYDROCARBONS Filed June 8,1949 .5 Sheets-Sheet 3 INV-ENTOR Patented June 20, 1950 UNITED STATESvMETHOD OF TEMPERATURE CONTROL IN NITRATION F HYDROCARBON S Leonard A.Stengel, Terre Haute, Ind., assignor to Comercial Solvents Corporation,Terre Haute, Ind., a corporation of Maryland Application June 8, 194:9,kSerial N o. 97,833

Thepresent invention relates to a process for the vapor phase nitrationof the lower saturated hydrocarbons, and more particularly to a methodwhereby the temperature of the nitration reaction is convenientlycontrolled by the addition to the reaction zone of oxygen, air or othergaseous mixtures containing free oxygen as more particularly describedhereinafter.

This case is a continuation-in-part of my application, U. S. Serial No.685,956, led July 24, 1946.

In carrying out vapor-phase nitration of saturated hydrocarbons in thepast, it has been the practice to separately vaporize the hydrocarbonsand nitric acid, and after mixing the reactants in a mixing chamber,passing the combined vapors into a reaction chamber in which is suppliedadditional heat suicient to bring the mixture to the reactiontemperature, thereby causing the components to react to produce thedesired nitrohydrocarbons.

This prior art practice was subject to a number of disadvantages. Notonly is the nitration reaction an exothermic one, but it is a reactionwhich proceeds favorably only within a relatively narrow temperaturerange to give optimum yields of nitrohydrocarbons. Thus, althoughnitration will occur to some extent in a relatively wide ternperaturerange between approximately 360 C. to 480 C., it is only within therelatively much narrower range of about 390 C. and 460 C. that optimumnitrohydrocarbon yields are obtained. Accordingly, it is necessary,after the initiation of the nitration reaction, to remove the heat ofreaction rapidly enough and to such an extent that the favorablereaction temperature range is not exceeded and yet not to remove so muchheat that the reaction mixture is cooled below its favorable reactiontemperature. This thermal control was formerly accomplished by immersingthe reaction chamber in a heat absorption jacket or bath such as a saltbath to absorb and convey away the excess heat of reaction. Such anoperation was not only wasteful of heat and heat transfer, but due tothe extreme rapidity of the reaction it was often impossible to removethe generated heat rapidly enough to prevent high temperatures frombeing reached, with resulting lower nitrohydrocarbon yields.

Another disadvantage of the prior art practicev was the low mole ratiosof hydrocarbon to nitric 13 claims. (c1. 26o-644) y l 2 acid, up toperhaps 40 to l, the higher the yield of 'nitrohydrocarbona But thesehigh mole ratios were uneconomic to maintain in the prior `is describeda marked improvement in the above acid that could be economicallyemployed with y the prior practice of mixing the vapors before passingthem into the reaction chamber. The

higher the mole ratio of hydrocarbons to nitric.

ystantial decomposition.

art system, because of the excessive amounts of unreacted hydrocarbonswhich had to be recovered from the reaction products. In the prior artpractice, the highest mole ratiosofhydrocarbon to nitric acid whichcouldbe economicall used was about 6 to 1.

In my joint patent, U. S. Patent No. 2,418,241,

described process, wheheby the reactants are mixed, the nitric acidreactant vaporized, and the reaction effected all in a single combinedvaporizer-reaction chamber. In accordance with the process described andclaimed in that patent, only the hydrocarbon reactant is preheated, andthen successive limited portions of liquid nitric acid of predeterminedconcentration are mixed therewith. The heat ofthe ensuing nitrationreaction is utilized to vaporize additional nitric acid, and is thusdissipated and largely controlled within the reaction system to maintainthe temperature within the narrow optimum range necessary for bestnitration results.

While the process disclosed in the above patent constituted a decidedimprovement over all prior art methods for the production ofnitrohydrocarbons, it likewiseI is subject to certain materialdisadvantages. In order for the reaction temperatureto be eiectivelycontrolled, the nitric acid used in that process must necessarily be ofa concentration within the range of rl0-0%. When less concentratednitric acid is used, the heat of reaction (between nitric acid andhydrocarbons) does not furnish sunicient heat, even when combined withthat heat introduced by the preheated hydrocarbon, to maintain thetemperaturek high enough for eiective vaporization of nitricacid and forthe reaction Aof the nitric acid with the hydrocarbons to take place. Inother words, when dilute nitric acid is used, a substantial portion ofthe heat is required to vaporize the water-contained in the acid and ittherefore becomes necessary to add additional external heat. Owing tothe high heat of the vaporization of water, it is not feasible tovaporize dilute nitric acid at a rate sufficient to provide the desiredratio of nitric acid to the quantity of hydrocarbon fed, if all the heatis to be supplied in the form ofsensible heat with the hydrocarbon.` Todo so would require heating the hydrocarbon to such an excessive hightemperature as to cause its subF It is therefore necessary in the aboveprocess to use nitric acid in at least about l-80% concentration byWeight. Such acid, unfortunately, is substantially more expensive thanthe less concentrated acid, and cannot be used ordinarily for economicreasons. On the other hand, it is difficult to supply a major portion ofthe required heat through the `reactor Walls,-owing vto the poor heattransfer, particularly if thefreactor` is supplied with acorrosion-resistant inner liner.

Moreover, in order to transfer any large quantityl vof heat through thewalls, it would be necessary to heat the walls to a substantially.higher ternperature than the mixture of reactants, thus producing alocalized overheating of I`the materials nearest the Walls, which isknown to have 'a highlydetrimental eiect on the reaction.

I have now found that tl'ieprocess` ,described y and claimed in U. S.Patent No.` 2,418,241 may be operated efficiently and economically, with40-70% nitric acid, by introducing oxygen, air or "other..,gaseousmixtures containing free4 oxygen into. the reactor ashereinafter'specied. In ac- 'cord'ance :with my vinvention the optimumtem-` peratures are maintained in the reactor atvall .'c'lopr'opane,vcyclobutane, 'cyclohexana methylcyclohexane, and dimethyl cyclohexane.

In ione specic embodiment of my invention, Ythe vaporizationlof nitricacid andthe reaction of the `nitric acid vapors with a hydrocarbon gasis carried out inthe apparatus diagrammatically represented by Figure I.Nitric acid is 4:pumped lthroughppe 4 supported by flange 5 into spraynozzle 6, from which it emerges asfa .n'emist into an`elongated-'cylindrical vessel 8, equipped'w'ith a corrosion-resis'tantvinner liner 9, 'an-'electrically Ainsulating outer covering l2, a spiralwinding l-3 `of resistance wire'a's asupplementary heat source if'additional heat is desired, and an outer covering |4 ofaAthermal-insulating material. A temperature 'recorder and controller I6is also provided, connected-to thermocouplesl'. The relcorder andcontroller I'E Aare-set so that Awhen the temperature Within the reactorfalls b'elovvv a `predetierinined figure, valve I1 'is opened to allowthe oxygen-containingl -gas to be introduced through pipe v2. VLikewisewhen the temperature is raised to the predetermined g'ure by thelib-Vera-tion of Iheat from the oxidation of hydrocarbons, valve vll 'is-closed by theopera'tion of temperature "controller lfS to cut off thesupply? of air. The preheated hydrocarbon gas is' introduced throughpipe Overheating vof vthe spray 'nozzle by Vthe hot hydrocarbonV gas isprevented by Aa cylindrical spray-nozzle protection baille' 1. lVIix-`ing of Vthe hydrocarbon gas, oxygen-containing 4 mic, the temperaturemay, after the reaction has proceeded for a time, exceed thepredetermined setting, causing controller I6 to stop the flow ofoxygen-containing gas by closing valve I1. The temperature is thereforecontrolled throughout the process by the introduction ofoxygen-containing'gas onlyas it is required to maintain the temperaturewithin the predeterminedy range.

The reaction mixture passes out of the apparatus through pipe l l,supported by ange l0, and is lrapidly cooled and subsequently treated tosep- .fara'te 'the various" constituents.

Alternatively, I may introduce the oxygen-con- -taining-gas asa mixturewith the preheated hyf1-5^v introduce'all or'part of theoxygen-containing gas `vdroc'arbon)gasr lthrough pipe l or 2. Or, I mayWithinv the cylindrical spray nozzle protection baille 1 through pipe 3supported by flange 5. In the lat-ter modication, the introduction ofcold gas through pipe 3 i's a particularly effective means forlpreventing any tendency of the spray -nczzle 6 to' overheat.

A Iuseful m'odica'tion of the a-bove lapparatus vcomprisesI providingrmeans lfor cooling the reactants after theinitiation of thenitrationrreaction, such` as by Tacl'letng the lower portion of Vthereactor with `a heat-transfer liquid; or by constructing the lowerportion in the form of a tube 'or V`coil and immersingit in a salt bath`maintained at a suitable temperature; o'rby quenching with a coolergas, such as steam, additional hydrocarbon' or 'an 'inert gas.

In another speciiic embodiment on my inven- 'timLth-e vaporization ofnitric acid and the reaction of vthe nitricacid vapors with ahydrocarbon gas is 'carried' out in an apparatus represented by li'gureIl. rThis apparatus comprises areaction chamber or :chambers I0,desirably insulated bysjackets H, the chambers -being arranged either asseveral separate connecting units as in Figure II, or asa single unit. YA pre'- hea'ter `'l2 forheating the hydrocarbon reactants lcomprises4any suitable heating p element 'and an inlet le for the vcold alkane. Agas conveyor 't3 `leads to y'lriydro'czn'bon linlet V2l of reactionchamber Hl." f, Reaction chamber` l0 is furtherprovided Vwith a primaryinlet I4, for the rst injection of liquid ynitric acid disposed Ain thepath 'of then-coming igaseous reactant and vslightly beyond theyhot-'gas inlet. Other `supplementary reactant inlets V22fare disposeda-t yintervals `through the extent 'of the lreaction-chamber, or in eachof r"the ysevera-l"connecting chambers. Externalv heaters L5 may bedisposed at intervals, if desired. lA lt'ernperatl'ire -recorder andcontroller 'il is also provided, connected to th'ermoc'cn'iplesI"261..The' temperature controller l also Vfcc''nnec'ired with, and 'controls'a valve Sil Whichin tur "ontrols thev `introduction Vofoxygencontainihg' ases, through pipe'y I6,V as needed.- 'A' corro onresistant lining 23 may be "provided.Within-the reaction chamber t6.,Be-

vgas :and nitric acid Ymistftalzes place -belovvjth'e jcyflinc'lricalspray protection rbaille-'1, whereupon the heat supplied bythe enteringgas and by the -electrical resistance* coil yaround 'the reactor, if

Vsuch a coil is used, and 'by the partial oxidation of thehydrocarbongas brings about the'vaporization of the nitric acid and Ainitiates, thenitration l"1"'eacti: n. YSince the Anitralton reactionisi'exother- -u'nchamber may 'be 'a'- singie unit within pmv nitr ator.

-rality ofV .inlets for the v.nitric acid or may comthrough pipe I6,andthe needed heat is released inr situ by oxidation of `a;,`portion ofthe hydrocarbon.` f y' If a plurality of interconnected reaction cham#-bers is utilized, and jnitric acid introduced in f each, additionalthermocouples 26, temperature controllers Il, valve 39, and pipes I6 arepro- `Vid'edtc introduce oxygen-containing gases into each chamber.

vThe rate of flow of hydrocarbon is regulated relative to the rate ofaddition of nitric acid such that the effective mole ratios ofhydrocarbon to nitric acid are in excess of 6 to 1 and preferablyconsiderably higher, preferably between aboutlO to 1 and 40 to 1.lRelatively somewhat higher molel ratios should be used in the case ofmethane and* ethane than with the other lower hydrocarbons because ofthe lower specific heat of these two hydrocarbon Imembers. For the lowerhydrocarbons votherthan `methane and ethane, a mole ratio between about20 to l and 30 to 1 is generally to Ybe preferred while with the lowermembers the-optimum eiective mole ratio is somewhat higher.

Y The number o-f additions of acid will in general determine the overallmole ratiol system, that the mole ratio of a quantity of hydrocarbonwith` respect to the total quantity of nitric acid introduced in all theseveral reaction chambers or at the successive intervals in a singlereaction chamber. Fromthe point of view of recovery of unreactedhydrocarbons, it is desirable to oper- 1ate at as low as possibleoverall ratio of hydrocomes in contactwith fresh nitric acid and whenthis concentration reaches a high enough point, reaction anddecomposition of the nitrohydrocarbon begins to take place. The numberof additions should be limited so as to maintain an overall ratio ofhydrocarbon to nitric acid of riot more than about 6 to 1, butpreferably not vvless than about 3 to 1 as the presence of about thisexcess of hydrocarbon is necessary to foster efficient progress of thereaction.

, The rate of introduction of nitricv acid and hydrocarbon and the ratioof nitric acid to hydrocarbon remains constant throughout the operationof the process for best results. Only the introduction of theoxygen-containing gas need be varied,v that is, larger quantitiesareintroduced when the temperature drops considerably, while smallerquantities are introduced to correct slight drops in temperature.

. Still another variation of my invention lies application to theso-called fluid bed type One modification of this type reactor is'diagrammatically shown in Figure III. ,Y In acfcordance with thisprocess; a mixture of hydrolcarbon'and either nitric acid or nitrogendioxide in therrequired reacting proportions is passed upwardly througha mass of luidized, heated, finely-divided solid material in such manneras to cause the latter to behave like a liquid. The particles shouldpreferably be powdered silica glassy havinga size within the-range 0-200mi- ;crons. By passing thereactant mixture upwardly through theiinely-divided mass of solid particles,l of substantially-uniform size,and by suitably regulating the rate of flow, the particles assumelimited freedom of motion and the whole has the appearance andA physicalproperties simi ilar to those of a boiling liquid.

Referring to Figure III, the nely-divided inert is stored in the powderstorage 3. The reactor 9 is'preferablyconstructed in two sections, thelower of which contains a' heating, element 8. The upper portion I2 ofthe reactor contains lters to prevent the loss of the fluidizing agent.In order to start the operation, the heater 6 is started and powderblown from the storage tank 3 through line ii into the reactor tube,prefer'- ably by means of hydrocarbon gas passed'into the powder storagetank through line 2. As soon as the lower section 6 of the reactor'ispartially lledwith powder, the flow of preheated hydrocarbon gas isstarted through line 5. Introduction of thepowder and hydrocarbon iscontinued until the reactor tube is lled to the proper height with thefluidized mass. Whenthis c'ondition is reached and the fluidized mass isheated to the desired reaction temperature, the ilow of liquid nitricacid is started into the convertor through the line I, the acid beingadmitted into the convertor through either or all valves (1, 8, I andII). The reaction then proceeds with additional heat being liberated asrequired', in situ, by oxidation of hydrocarbon gas. Fortemperaturecontrol, the reactor is equipped with thermocouples Il, connected to atemperature recorder and controller I8. When additional heat isrequired, that is when the temperature in the reaction zone falls belowa predeterminedy gure, controller I8 causes Valve I9 to open, thuspermitting oxygen to enterthe reactor through line 20.

After completion of the reaction, the reaction gases pass through lineI3, then to cooler I4 where the temperature of the gases is lowered asrapidly as possible and then passed into the condenser I5 where theliquid condensate is recovered through line I6.

It is distinctly understood that the apparatus are purely illustrative,and are in no way intended to limit the application of my process to anyspecic types of apparatus.

I have found that, in any of the nitrators specied, the temperature ofthe reaction chamber will be raised to the desired reaction ternperaturewhen air or other free oxygen-containing gas is added, only if thetemperature is above about 250 C. before the addition of the freeoxygen. At temperatures below about 250 C., oxidation of thehydrocarbons proceeds very slowly, even in the presence of vaporizednitric acid. It is therefore necessary to raise the temperature to aboveabout 250 C. before introducing the free oxygen. This may beaccomplished by applying additional external heat, preheating theentering hydrocarbon gas, 'and the like.

In'the nitration of hydrocarbons by my process I have foundvthat theaddition of gases con- 7 taining -free oxygen :to ythe reaction mixturefor the purpose Tof supplying 'additional' `heat `when required producesncvsuhs'tantm `alterar-.ion vin the reaction conditions required Aforthe maxitemperature of reactionsat about 420 C. 'average o'f 40l'cu.ift/hr. of air was-required for this-purpose. hsthe product'emerged fromthe vdoot'to'rn 'o'f 'theappara'tus, vit was rapidly cooled, `and lfromit was separated .7.85 :poundskper hour having an 'inside `diameter of2;5 inches, were .pumped 8.5 'pounds :per lhour of fadueou's 46% nitricacid. Concurrently therewas :introduced 4150 lcu. Ift./hr. -of rpropaneYpreheated to '400 -C The pressure 4Within the 1:apparatus wasmaintainedat '75 p. s. i. gage. Air, preheated `"to 350 mum output 'o'nitrohydrocarbons. Pressures f5 vrrangingfrom vatmospheric up to as highas 1,000 o'f 'fan organic layer having the following com- '1bs. per sq.in. have been lfound suitable. The Lp'osition: f operative maximumvtemperatures 'within the .-ref i Percent by weight action -zone varysomewhat depending I'on the -liowboilers v y 13.1 hydrocarbon, andthecontact timeiis lan inverse ".10 Nitromethaiie .11311 function of thetemperature. Of 'the three Ilow- Nitr'oethane 16:2 est boilinghydrocarbons, the Sfollowing approxi- L2-nitropropane Y 32.40 materanges are suitable: 1-nitroprcpane '38.-'0

` Seconds i o 1 -From the `foregoing results, 1t was calculated 'Methane375-5500 C .1o-m32 15 that the nitrohyaredart-rms "had been producedEhane 30a-5%() .m 'goom f 1n aconversion of"3'1% of theory, based'onthePropane 300- 00 C'"`"''""'' nitric acid fed into the reactor.

In general, best results lare obtained when 'the reaction temperature.maintained within the 1 n range 390-460o C. 20 lThis run .Was made inan apparatus conf- The proportion of oxygen-containing ses 'and structedas illustrated in Fig. "II, except that 5 the temperature 110 Which 15h@hyd-FOCSJIDOHS `and separate connecting units Were arranged hside by theOxygen-containing gas -should be preheated side. 10,500 cu. .it/hr. ofnatural gas, .preheated are interdependent variables that are greatly-to 450 C., was introduced into the rst unit at aiecte'd by theconcentration of nitric acid, the 125 inlet 2| Cold 70% nitric acid waspumped to 'type .of hydrocarbon, and the 'rate of heat 'loss each inlet(i4 and'z) at the rate of 57.1f1bs.per from Athe Walls of theVaporizer-reaetor vessel. hour, '-110 maintain Steady temperaturesthrough- It is necessary to supply sufficient heat in the out thereactor, that ris to `hold the exit end of form of sensible heat of theentering gaSeS. the each vaporizer-reactorat approximately 455 C., -heatof combustion of a portion of the vhymoal- "30 air was introducedthrough inlets |"6 as required. 130115, ndQf desir-ed, heat 'from anSLIXISJYX- The air consumption averaged 563 it/hr. A terna). OI'internal e1C7Ca1 resistance J(S0-i1, t0 .product having .the fouowingcomposition was vaporiz'e the nitric acid completely and to h'eatWithdrawn "from the .last unit; the resultant mixture of gases 'to thet'en'ipera- Per cent ture at 'which the nitration reaction is initiated,"35 Low boilers- 3.1 'as specified above.y vThe spe'cic heats and -JtheNitromethane 45.6 heats of combustion of the various hydrocarbons,Nitroethane 26.5 land the specific heat and heats of vaporiz'ation .zmtropropane 79,8 Vof Water and nitric acid, are readily available in ynitropropane 105 the literature, and it win be obvious 'to those '40.Nitrobutane 4.2 skilled in the art howto oarryout such calculaf f Y ytions. The renewing specific examples "inus- T1?? eveeeejconvelswn t0111005115211185. based trate the coordination of Lthe several variablesin on 'mtnc amd fed Was 158%- my process: EXAMPLE I A Series of runs wasmade in the 'same appa- Into an apparatus, constructed 'asillustrated inratus described v'in EXamle II, under the condi- Figure I, and having aDur'ro'n vcorrosion-re'sisittions and with the results shown'in theo'llo'wing ant liner 9 measuring 24 inches in length and t table:

Table I v14.1010 Aid'red .C6-faam Am .Air Ave' Tempe C -xveraigeHydrocarbon'Composition Hydrgarbon Strength Pom-lds Time, Consump-Conversa@ Fed cFH Wilfr loglzher Seconds; tion 0F11 3,11%??? Natural gas10,600 f f 07 1,81 f .125.7 B65 A42 Y 466 )954s De. 10,180 66, 21:1,k2551 865 i443` 465: 12.61 v D6 10,660 64 des .24el sos 437 =464 v.12. 1s91.6%Nat.g26+4%pr6pane ,020 y64 '189 :251 "478; u32 45T 21.30 y84.3%Nat. gas-145.7% propane; 10,1820 64 274 241 478 i. 420 I45() f I19.88Propane 1o, 100 55 ase 1111 4,920 ,443.v 466 134. 1 D 11,420 5016-60413. .i917A 1,490' Y423: '444 `32:5 `62 y457.y .11704:A I'430s 4521 34.111,140 64 `4,32 1060 1,780 410. 4:17v .36.18 10;-920 t 6s 1449 2100 1,700 j 4427'; '450 37.' o

1 Only lacid sprayunits u'sed.

The yforegoing examples lare illustrative only,

70 and arenot'tofbeconstruedfasflimiting my inven- `tion to the'specified apparatus, steps, 1o`r materials. In generaLfitfniay'be saidthatany 'modi'- lviications "or 'equivalents that 'would "ordinarily`occur to those 'skilled iin 'the :'arlt'are t'o be foon-C..wasintroduced, as requiredto maintain the l'75 sidere'd as lyingwithinfthelscopepfimy invention A'1'. In the manufacture oflowernitrohydrocarbons-'by nitration oflow-molecular saturated hydrocarbons,the improvement which comprises regulating the'- reaction temperature bythe introduction of regulated amounts of a gaseous mixture containingfree oxygen whereby the desired increase is produced by reaction withthe hydrocarbons.

2.. In the manufacture of-lower nitrohydrocarbons by nitration oflow-molecular saturated hydrocarbons, the improvement which comprisesmaintaining the reaction temperature within the range S90-460 C. by theintroduction of regulated amounts of a gaseous mixture containing freeoxygen whereby the desired increase is produced by reaction with thehydrocarbons.

3. In a continuous process for manufacturing lower nitrohydrocarbons bythe vapor-phase nitration of low-molecular saturated hydrocarbons, theimprovement which comprises introducing regulated amounts of a gaseousmixture containing free oxygen into the reaction zone to maintain apredetermined temperature within the range S90-460 C. whereby thedesired increase is produced by reaction with the hydrocarbons.

4. In a continuous process for manufacturing lower nitrohydrocarbons bythe vapor-phase nitration of low-molecular saturated hydrocarbons, theimprovement which comprises maintaining the temperature of reactionwithin the range S90-460 C. by introducing a gaseous mixture containingfree oxygen into the reaction zone when said reaction temperature dropsto a predetermined temperatur-e below this desired range, said oxygenbeing added in quantities sufcient to bring said temperature within therange 390- 460 C. upon reaction with said hydrocarbons.

5. In a continuous process for manufacturing lower nitrohydrocarbons bythe vapor-phase nitration of low-molecular saturated hydrocarbons, theimprovement which comprises maintaining` the temperature of reaction ata predetermined temperature within the range 390-40 C. by introducing agaseous mixture containing free oxygen into the reaction zone when saidreaction temperature drops to a predetermined temperature below thisdesired range, said oxygen being added in quantities sufficient to bringsaid temperature within the range S90-460 C. upon reaction with saidhydrocarbons.

6. In a continuous process for manufacturing lower nitrohydrocarbons byheating low-molecular saturated hydrocarbons to a temperature within therange of about Bim-460 C., continuously passing the heated hydrocarbonsin vapor form into one end of an elongated reaction Zone, introducingliquid nitric acid having a concentration between about 40-'70%, in afinely dividedstate into said reaction zone in contact with the heatedhydrocarbon, whereby said nitric acid is vaporized and reacts with saidhydrocarbon, the improvement which comprises maintaining the reactiontemperature between about S90-460 C.

by introducing a gaseous mixture containing free oxygen into saidreaction zone when said reaction temperature drops to a predeterminedtemperature within the range 25W-460 C. said oxygen being added inquantities suilicient to bring said temperature of the reaction zonewithin the range 390-460 C. upon reaction with said hydrocarbon.

7. In a continuous process for manufacturing nitropropanes by heatingpropane to a temperature within the range of about S90-460 C.,continuously passing the heated propane in vapor form into one end ofan.elongated'reaction zone, introducing liquid nitric acid having. aconcentration between about 40-'70%, in a iinely divided state into saidreaction Zone in contact with the heated propane, whereby said nitricacid is vaporized'and reacts with said propane, the improvement whichcomprises maintainingl the reaction temperature between about S-460 C.by introducing a gaseous 'mixture containing'free oxygeninto saidreaction zone when said reaction temperature dropsto a predeterminedtemperature within 'the range'250-460F C., said 'oxygen being added' inquantities'surlcient `rto bring 'said temperature of the reaction z'onewithin rthe range 39o-460 C. upon reaction with said propane.

8. In a continuous process for manufacturing lower nitrohydrocarbons bypassing nitric acid and low-molecular saturated hydrocarbons through aluidized mass of heated finely divided silica glass, the improvementwhich comprises regulating the reaction temperature by the introductionof regulated amounts of a gaseous mixture containing free oxygen wherebythe desired increase is produced by reaction with the hydrocarbons.

9. In a continuous process for manufacturing lower nitrohydrocarbons bypassing nitric acid and low-molecular saturated hydrocarbons through aluidized mass of heated nely divided silica glass, the improvement whichcomprises maintaining the temperature of reaction within the rangeS90-460 C. by introducing regulated amounts of a gaseous mixturecontaining free oxygen whereby the desired increase is produced byreaction with the hydrocarbons.

10. In a continuous process for manufacturing lower nitrohydrocarbons bypassing nitric acid and low-molecular saturated hydrocarbons through auidized mass of heated finely divided inert solids, the improvementwhich compri-ses maintaining' the temperature of reaction within therange S90-460 C. by introducing a gaseous mixture containing free oxygeninto the reaction zone when the reaction temperature falls to apredetermined temperature within the range Z50-460 C., said free oxygenbeing added in quantities suicient to bring said temperature within therange S90-460 C. upon reaction with hydrocarbon.

11. In a continuous process for manufacturing lower nitrohydrocarbons bypassing nitric acid and low-molecular saturated hydrocarbons through afluidized mass of heated nely divided silica glass, the improvementwhich comprises maintaining the temperature of reaction within the range390-460o C. by introducing a gaseous mixture containing free oxygen intothe reaction zone when the reaction temperature falls to a predeterminedtemperature within the range Z50-460 C., said free oxygen being added inquantities sufficient to bring said temperature within the range S90-460C. upon reaction with said hydrocarbon.

12. In a continuous process for manufacturing nitropropanes by passingnitric acid and propane through a iiuidized mass of heated iinelydivided inert solids, the improvement which compri-ses maintaining thetemperature of reaction within the range 390-460 C. by introducing agaseous mixture containing free oxygen into the reaction zone when thereaction temperature falls to a predetermined temperature within therange Z50-460 C., said free oxygen being added in quantities suiiicientto bring said reaction temperature 11 within the range 390460 C. uponreaction Awith said propane.

13. In the manufacture of lower nitrohydrocarbons, the process whichcomprises preheating propane to a temperature of about 400 C. preheatingair to a temperature of about 350 C. con` tinuously `passing thesepreheated gases at a pressure of about '75 pounds per square inch intoan elongated reactionv zone, continuouslyv spraying aqueous nitric acidhaving `a concentration of about 4=6%;intor the mixture'of propane andair in said zone; the said propane, air and nitric acid being passedinto said reaction zone at the ratios of about 450 cubic feet per hour'of propane,

40 cubic feet per hour of air and 8.5 pounds of LEONARD A. STENGEL.

No references citedv

1. IN THE MANUFACTURE OF LOWER NITROHYDROCARBONS BY NITRATION OFLOW-MOLECULAR SATURATED HYDROCARBONS, THE IMPROVEMENT WHICH COMPRISESREGULATING THE REACTION TEMPERATURE BY THE INTRODUCTION OF REGULATEDAMOUNTS OF A GASEOUS MIXTURE CONTAINING FREE OXYGEN WHEREBY THE DESIREDINCREASE IS PRODUCED BY REACTION WITH THE HYDROCARBONS.
 13. IN THEMANUFACTURE OF LOWER NITROHYDROCARBONS, THE PROCESS WHICH COMPRISESPREHEATING PROPANE TO A TEMPERATURE OF ABOUT 400*C. PREHEATING AIR TO ATEMPERATURE OF ABOUT 350*C. CONTINOUSLY PASSING THESE PREHEATED GASES ATA PRESSURE OF ABOUT 75 POUNDS PER SQUARE INCH INTO AN ELONGATED REACTIONZONE, CONTINUOUSLY SPRAYING AQUEOUS NITRIC ACID HAVING A CONCENTRATIONOF ABOUT 46% INTO THE MIXTURE OF PROPANE AND AIR IN SAID ZONE; THE SAIDPROPANE, AIR AND NITRIC ACID BEING PASSED INTO SAID REACTION ZONE AT THERATIOS OF ABOUT 450 CUBIC FEET PER HOUR OF PROPANE, 40 CUBIC FEET PERHOUR OF AIR AND 8.5 POUNDS OF NITRIC ACID PER HOUR; CONTINUOUSLYWITHDRAWING THE RESULTING REACTION PRODUCTS FROM SAID REACTION ZONE ANDRECOVERING NITROHYDROCARBONS THEREFROM; THE CONDITIONS OF THE REACTIONBEING SUCH THAT THE REACTIONMIXTURE REACHES A TEMPERATURE OF ABOUT370*C. AFTER COMPLETE VAPORIZATION OF THE NITRIC ACID AND A TEMPERATUREOF ABOUT 420*C. BEFORE PASSIN GOUT OF THE REACTION ZONE.